1. Field of the Invention
The present invention relates to a device for producing an imaging element by peeling apart an image-receiving sheet from an image-bearing sheet laminated thereto subsequent to the exposure of said image-bearing sheet, for example, by means of laser radiation.
2. Description of the Prior Art
Several proposals have been disclosed so far for obtaining an imaging element suited for development by dry processing with the main purpose of avoiding the use of any processing liquids.
In addition to its substantial environmental advantages, dry processing, offers the considerable benefit of being suited for use under regular room illumination. However, these features are counterbalanced by the relatively low sensitivity and the high-power of the exposing equipment involved in dry processing.
The latent-image formation commonly occurs by introducing selective adhesion differences between the density-producing and the image-bearing layers by means of an imagewise heat treatment. The processing, or visible-image formation, may be performed by a sequential laminating-delaminating step of a sheet material against the image-bearing surface of a recorded film. The imaging material, as described e.g. in EP 93 201 858, generally comprises a transparent sheet bearing an imaging layer. The imaging layer is covered with a release layer and a thermosensitive adhesive layer having a second-order transition temperature ranging from 20.degree. to 60.degree. C.
The processing occurs by laminating a transfer sheet material to the thermosensitive adhesive layer under pressure and at increased temperature. Such transfer sheet material may be any coated or uncoated paper type, polyester or any other flat base. The visible image is produced by peeling apart again the laminate of the two above-mentioned sheet materials, i.e. the image-bearing and the transfer sheet materials. During the peeling-apart or delamination process the imagewise recorded areas of the imaging and release layers are left on the transparent base. The non-image areas, i.e. the layer areas that have not been imagewise recorded, together with the release layer remain adhered to the transfer sheet material. As a result of the peeling-apart process two complementary images are generated. i.e. one on the transparent base and the other on the transfer sheet material.
For the following reasons, it is essential to apply a sufficiently high amount of heat to the sheet materials within a relatively short period of time:
(1) achievement of the highest possible production speed; PA1 (2) achievement of a range allowing lamination and delamination to take place at the same speed; and PA1 (3) achievement of a speed range for obtaining optimum image quality irrespective of the materials used. This can be realised by exposing the transfer sheet material and/or film material either for a short time to a high temperature or for a prolonged time to a lower temperature. A sufficient heat supply to the thermosensitive adhesive layer is required for heating it to above its second-order transition temperature so that it softens and exhibits its adhesive behaviour. PA1 (1) the low end of the speed range is restricted by a specified minimum production speed and speed-dependent image quality; and PA1 (2) the upper end of the speed range is restricted by the practicalities of accelerating from standstill or low speed to high speed. PA1 (1) initiation speeds ranging from 1 to 20 m/min, and PA1 (2) delamination speeds varying between 1 and 10 m/min.
For the same reasons, the initiation or start of delamination and the actual delamination or peeling-apart of the two sheet materials at the delamination side should occur at the highest possible speed. However, there are the following restrictions:
It has been found that practical values for operating speeds are as follows:
Devices for realising the peeling apart of two bases laminated together have been disclosed in the Belgian Patent Application No 93 01277 filed on Nov. 19, 1993.